Open phpMyAdmin or mysql command line client, choose database pma and execute query:
USE psa; SELECT REPLACE( sys_users.home, '/var/www/vhosts/', '' ) AS domain, sys_users.login, accounts.password FROM sys_users LEFT JOIN accounts ON sys_users.account_id = accounts.id ORDER BY sys_users.home ASC
It will show you all FTP users from Plesk
There is 2 steps.
First of all, add to /etc/proftpd.include followed code:
TimeoutIdle 900 TimeoutNoTransfer 900 PassivePorts 49152 65534 TimesGMT Off
Then test the iptables nat helper:
modprobe ip_conntrack_ftp
If there is no errors, add to directive IPTABLES_MODULES in /etc/sysconfig/iptables-config module ip_conntrack_ftp:
IPTABLES_MODULES="ip_conntrack_ftp"
If you need to load two or more helpers, separate them with spaces because the iptables script does a for-in on the IPTABLES_MODULES directive.